Niice. If it starts, twist the oil cap on the valve cover and let it sit. If it rattles and you see lots of oil vapor blowing, then there is blowby.
Hopefully you don't see that. oversize pistons are unavailable. If you find them, please let me know. I have a clean, resleeved block that
got bored out just a skosh too big.
Fresh fuel lines including the "cigar", the 2 filters, and a tight, new primer pump are key to smooth running. Also, there's a filter
in the tank pickup that might be gunked with algae.
Besides the oil pans, the oil filter housing where it attaches to the block and the turbo return line where it attaches to the top pan are likely sources of leaking.